The Noah et al. patent discloses a pneumatic actuator having a single service piston that applies the braking mechanisms of passenger railway transit vehicles and the like. The service piston of Noah et al. has a hollow stem located around a threaded shaft provided with power and brake adjusting collets threaded on the shaft. The brake adjusting collet provides adjustment for excess wear of brake shoe and other components of the transit vehicle. The disclosure of the Noah patent is incorporated herein by reference.